RU2660819C1 - Method of manufacturing a super-capacitor electrode - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: invention relates to electronic engineering, in particular to methods for manufacturing supercapacitors. Method for manufacturing the supercapacitor electrode is to apply a buffer layer, a catalytic bed, a dielectric layer, an insulating layer in the dielectric layer of the window matrix to a catalytic bed with a cross-sectional dimension of 40–60 mcm, deposition in the windows of arrays of vertically oriented carbon nanotubes, the functionalization of the surface of carbon nanotubes by oxygen-containing groups, the layer formation of polyaniline containing the isotope C-14, on vertically oriented carbon nanotubes by electrochemical deposition, annealing.

EFFECT: invention provides a self-charging function in a supercapacitor.

13 cl, 2 dwg

Description

The invention relates to electronic equipment, in particular to methods for manufacturing supercapacitors. The invention can be used in the energy sector, when creating highly efficient generators and electric energy storage devices that can work autonomously for a long time, in autonomous mobile miniature low-current power sources used in microelectronics systems.

Supercapacitors are some of the most promising energy storage devices. Supercapacitors usually have a design of two polarizable electrodes, separated by an ion permeable separator impregnated with an electrolyte. The disadvantages of many known supercapacitors are the need for charging from an external power source.

Known US patent US 2858459 (IPC G21H 1/04, published 28.10.1958), which describes a capacitor consisting of two spherical plates, one of which is inside the other larger diameter. On the inner lining there is a beta radiation source, from which this capacitor is charged. The disadvantage of the above device is the large size and weight, low power and low current during continuous operation.

It is known that the capacitor electrode is made of carbon fiber material and is metallized with nickel, as described in RF patent RU 2058054 (IPC H01G 9/04, published April 10, 1996).

It is known that electrodes of a capacitor with a double electric layer are made of an elastic material consisting of a mixture of activated carbon particles containing large and small particles, a porous elastic dielectric and a polymer binder, which are used as polyalcohols and polysaccharides (RF patent RU 2041518, IPC H01G 9 / 04, published 09/08/1995).

A known method of manufacturing a capacitor with a double electric layer according to the patent of the Russian Federation RU 2172037 (IPC H01G 9/058, H01G 9/155, published 08/10/2001), comprising mixing activated carbon and a thermoplastic polymer, followed by pressing and heat treatment, where the thermoplastic polymer is taken with a bulk density of 0.05-0.19 g / cm ³ and an average particle size of 0.1-1.2 of the average particle size of activated carbon, which is taken with a bulk density of 0.2-9.0 of the bulk density of a thermoplastic polymer at the ratio of the bulk volume of activated carbon to bulk volume of thermoplastic polymer (6.0-0.7): 1. As the polymer used polyethylene.

A known method of manufacturing a supercondenser electrode, comprising mixing activated carbon, an electrically conductive additive and a polymer binder with an organic solvent, compacting the mixture, followed by molding the active carbon base, heat treatment and metallization of the latter, the mixture is subjected to fibrillation before densification at a temperature of 50 ° C, and heat treatment is carried out at temperature of 100 ° C, while the mixture to obtain an active carbon base contains components in a certain ratio, and elec ronoprovodyaschaya additive consists of multi-walled carbon nanotubes and / or carbon black (patent of Russian Federation RU 2427052, IPC H01G 9/058, H01G 9/155, published 20.08.2011).

The closest in the set of essential features (prototype) of the invention for the device is the technical solution set forth in RF patent RU 2533010 “Method for manufacturing a planar capacitor of increased capacity”, IPC H01G 4/00, B82B 3/00, published November 20, 2014. A method of manufacturing a planar capacitor of increased capacity includes creating a first electrode by forming a conductive layer with a developed surface on a conductive electrode base, forming a thin dielectric layer uniform in thickness, repeating the surface relief of a conductive layer with a developed surface, filling voids with conductive material between the irregularities of the first dielectric coated electrode layer, thereby creating a second electrode, and a conductive layer with a developed surface of the forms It is formed from a material having an anisotropy of electric current conductivity such that in the horizontal direction electric conductivity is higher than vertical electric conductivity, the conductive layer with a developed surface is a carbon nanostructure in the form of columns and is formed by chemical vapor deposition stimulated by plasma. This layer contains metallic or intermetallic nanoclusters.

A known method of manufacturing an electrode material of the prototype does not provide for charging a capacitor from an internal beta radiation source. The columns are made of carbon nanotubes, which are not fastened together by a binder. Such columns in the longitudinal direction have a high modulus of elasticity, however, with transverse loads, they are easily detached from the substrate in view of low adhesion. Therefore, this design is not mechanically strong with respect to mechanical shear stress. In the known method, the space between the nanotubes in the column is not filled with a conductive substance, which reduces the electrical conductivity and thermal conductivity of the column. The column is covered with a dielectric, therefore, the capacitance of the supercapacitor (C) as a whole is determined by the area of the dielectric (S), its thickness (d) and dielectric constant

In the known invention, the property of branching nanotubes is not used (S.V. Bulyarsky, Carbon nanotubes: technology, property management, application, Ulyanovsk 2011, 432 pp.).

The value of the stored energy in supercapacitors (E) is determined by the value of its capacitance (C) and the potential difference between the electrodes that output current (U):

The power (P) that is released by the supercapacitor is determined by the potential difference between the electrodes that output current (U) and the series resistance of the electrodes (R):

In accordance with these formulas, the capacitance of the supercapacitor and the potential difference between its electrodes should be as large as possible, and the series resistance as small as possible.

The supercapacitor electrodes must satisfy at least two conditions, namely, have a large contact surface of the electrode material with the electrolyte, which provides a large capacity necessary for storing significant amounts of electrical energy, as well as high conductivity of the electrode material necessary for the release of energy in short intervals time. These conditions of the nanotube, which form the column according to the invention RU 2533010, are not fully satisfied.

Promising electrode materials for chemical current sources are nanocomposites containing carbon nanotubes (CNTs) and electrically conductive polymers (Wu T.-M., Lin Y.-W., Liao Ch.-S. Preparation and characterization of polyaniline / multi-walledcarbon nanotube composites // Carbon. - 2005. - vol. 43. - P. 734-740.). The introduction of carbon nanotubes into the nanocomposite allows, firstly, to increase the electrical conductivity of the material, and secondly, to create a structure with optimal porosity necessary to increase the capacity.

The technical problem of the present invention is the creation of a durable electrode with a branched surface, having a large area in a confined space, large electrical and thermal conductivity, capable of recharging the supercapacitor from an internal beta radiation source throughout the entire service life, thereby ensuring long-term autonomous use of the power source without supplying electric energy to it from the outside.

The technical result consists in the fact that the electrode provides the combination of the charging function of the capacitor from an internal beta radiation source, energy storage and storage in the supercapacitor, provides a high capacity and amount of stored energy, provides continuous charging of the supercapacitor for more than 260,000 hours in stand-alone mode without supply external electric energy, and also has a low electrical and thermal resistance of the electrodes, providing high discharge currents and the release of oplennoy energy in a short period of time.

To achieve the above technical results, in the method of manufacturing a supercapacitor electrode (ionistor), a buffer layer is applied to the conductive substrate, the catalytic layer, then the dielectric layer, the window matrix is opened in the dielectric layer to the catalytic layer with a transverse size of 40-60 microns, arrays of vertically oriented carbon nanotubes, carry out the functionalization of the surface of carbon nanotubes with oxygen-containing groups, form a layer of polyaniline containing the C-14 isotope, on vertically oriented carbon nanotubes by electrochemical deposition, then annealing.

The described sequence of actions leads to the formation on the surface of the electrode of an ordered matrix of columns of composite formed by an array of carbon nanotubes and polyaniline containing the C-14 isotope. The formed columns are radioactive and, as a result of beta decay of the C-14 isotope, emit electrons with energies from 5 to 140 keV.

The proposed electrode differs from the prototype in that the nanotubes in the columns are coated with polyaniline containing the C-14 isotope, as a result of electrochemical deposition of aniline monomers, form an electrically conductive and thermally conductive porous composite material with high electrical conductivity and thermal conductivity. The formed columnar structure has electrical and thermal contact of low resistance with a conductive substrate.

The production of polyaniline based on the carbon isotope C-14 leads to the fact that polyaniline acquires the properties of radioactivity and emits high-energy electrons from 5 to 140 keV. This property is due to the fact that the carbon isotope C-14 undergoes beta decay with the release of electrons that have high energy. The average energy of electrons arising from beta decay of the C-14 isotope is 49 keV, and their maximum energy reaches 140 keV. The high energy of the resulting electrons leads to the generation of pairs of positively and negatively charged ions in the electrolyte. The generation energy of one such pair is 2-3 eV. Therefore, one high-energy electron interacts with the electrolyte repeatedly and produces 20000-30000 of such pairs. Ions of the pair are separated by the electric field of a double electric layer, which is formed at the interface with the electrolyte when it contacts the surface of the formed columnar structure of a composite of vertically oriented arrays of carbon nanotubes and polyaniline. As a result, the supercapacitor acquires the property of self-charging.

The ordered arrangement of carbon nanotube arrays on the electrode surface provides: an increase in mechanical strength due to the fact that the bundles of nanotube arrays reinforce polyaniline, increase adhesion to the substrate, create a low-resistance electrical contact between the composite and the substrate, and provide good heat removal from the composite layer due to high thermal conductivity carbon nanotubes and low thermal resistance of the contact of the composite with the substrate. The diameter of the columns is determined by the mean free path of electrons emitted during beta decay in polyaniline. The distance between the centers of the columns is determined by the need for a gap between these columns. The selected geometry of the columns of the porous composite based on bundles of carbon nanotube arrays with polyaniline deposited on them provides a gap between the columns with a transverse size of 40 to 60 μm, which were formed as a result of the deposition of polyaniline on the surface of carbon nanotubes. Electrolyte freely enters this gap and into the pores of the composite, which is introduced when the electrode is assembled into the supercapacitor. Due to the porosity of the formed structure of the electrode, the surface branching increases in comparison with the prototype. An increase in the surface leads to an increase in the capacitance of the supercapacitor, since the capacitance is caused by a double electric layer, which is formed by the electrolyte upon contact with the surface of the columns formed on the basis of arrays of carbon nanotubes and polyaniline.

In the particular case of carrying out the invention, the height of the carbon nanotubes is from 30 to 100 microns.

In the particular case of the invention, the distance between the centers of the windows is 70-100 microns.

In the particular case of carrying out the invention, the functional oxygen-containing group is a carboxyl group.

In the particular case of carrying out the invention, the thickness of the buffer layer is from 5 nm to 60 nm.

In the particular case of the invention, the buffer layer is made of aluminum and / or titanium and / or titanium nitride.

In the particular case of carrying out the invention, the catalytic layer is made from a thickness of 0.5 nm to 20 nm.

In the particular case of the invention, the catalytic layer is made of iron and / or iron oxide and / or cobalt and / or cobalt oxide and / or nickel and / or nickel oxide and / or their alloys.

In the particular case of the invention, the dielectric layer is made of silicon oxide or silicon nitride,

In the particular case of the invention, the dielectric layer is made from a thickness of 0.5 to 3 μm.

In the particular case of the invention, the windows are square, or rectangular, or round.

In the particular case of the invention, before functionalization, an additional heat treatment is carried out.

In the particular case of the invention, annealing is carried out at a temperature of from 80 to 300 ° C and a pressure of from 0.001 to 1.02 bar.

In the particular case of the invention, the matrix of windows is made with the location of the centers of the windows in the nodes of a rectangular grid with a cell side of 100-120 microns.

The combination of features characterizing the invention allows to manufacture an electrode for a supercapacitor, which has high mechanical strength, high electrical and thermal conductivity, a large surface area and the ability to charge the supercapacitor due to the energy of the internal beta source.

The invention is illustrated by the following drawings:

FIG. 1 is a cross-sectional diagram of an electrode;

FIG. 2 - SEM images of bundles of carbon nanotube arrays at various magnifications grown on conductive substrates in windows opened in a dielectric layer.

A method of manufacturing a supercapacitor electrode (Fig. 1) includes the following operations: applying a buffer layer 2, a catalytic layer 3, then a dielectric layer 4 to the conductive substrate 1. Opening the matrix of windows 5 in the dielectric layer 4 to the catalytic layer 3. The size of windows 5 is 40- 60 microns. Deposition in windows of 5 arrays of vertically oriented carbon nanotubes 6. Functionalization of the surface of carbon nanotubes 6 with oxygen-containing groups, the formation of a layer of polyaniline 7 containing the C-14 isotope on vertically oriented carbon nanotubes 6 by electrochemical deposition. Carrying out annealing.

The height of the carbon nanotubes 6 is from 30 to 100 microns. The distance between the centers of the windows 5, in which form (grow) an array of carbon nanotubes, 70-100 microns. Windows 5 may be square or round.

A functional oxygen-containing group is a carboxyl group. Before functionalization, annealing is carried out to improve the quality of carbon nanotubes 6. The buffer layer 2 is made of a thickness of 10 nm to 60 nm from aluminum and / or titanium and / or titanium nitride, and the catalytic layer 3 is from a thickness of 0.5 nm to 20 nm from iron and / or iron oxide and / or cobalt and / or cobalt oxide and / or nickel and / or nickel oxide and / or their alloys. The deposition of the buffer and catalytic layers can be realized by the magnetron and / or electron beam method, and / or in another way.

The dielectric layer 4 is made of silicon oxide / nitride with a thickness of 0.5 to 2 μm. The deposition of the dielectric layer 4 can be realized by the magnetron, and / or electron beam method, and / or in another way.

Windows 5 in the dielectric are opened by the methods of planar technology using photolithography and etching.

The formation of vertically oriented bundles of carbon nanotubes 6 is carried out by plasma-chemical deposition from the gas phase. This method is implemented by introducing a substrate into a heated reactor, supplying a carrier gas and carbon-containing gas, and generating plasma. As the carrier gas, argon and / or ammonia and / or helium and / or nitrogen are used, the carbon-containing gas is methane, and / or ethylene, and / or acetylene, and / or carbon monoxide. The pressure in the reactor during the formation of an array of carbon nanotubes is set in the range from 60 Pa to 550 Pa, and the temperature in the range from 400 ° C to 800 ° C. To generate plasma, electromagnetic radiation with a frequency of 13.56 MHz and a power in the range from 10 W to 200 W is supplied to the reactor from the generator.

To carry out the synthesis, known plants of domestic and foreign production can be used. For this, substrates with deposited buffer and catalytic layers are placed on the holder in the loading chamber, the loading chamber is pumped out, then, using the loading device, the substrates are introduced into the reactor and placed on the surface of the working table heated to the required temperature. The reactor is pumped out to a pressure below 7.5 × 10 ^-3 Pa. Then, through the reactor, a flow of carrier gas (100 ÷ 600 cm ³ / min) and carbon-containing gas with a feed rate of 10 ÷ 100 cm ³ / min is provided. Immediately before the formation of carbon nanotubes, the pressure is stabilized to the desired value. A high-frequency plasma is generated with a given power of electromagnetic radiation from a generator. At the end of the synthesis of carbon nanotubes, the electromagnetic radiation from the generator is stopped, then the carrier gas and carbon-containing gas are stopped, the pressure in the reactor decreases to a pressure below 7.5 × 10 ^-3 Pa, after which the substrates are removed using the loading device into the loading the camera.

The transverse size of the column of nanotubes 30-60 microns (Fig 2). The diameter of the formed carbon nanotubes is from 4 to 90 nm, and the length is from 30 μm to 100 μm.

The functionalization of the surface of carbon nanotubes is carried out chemically in two stages. The first stage is treatment in 37% hydrochloric acid, the second stage is treatment in a mixture of 67% HNO ₃ + 98% H ₂ SO ₄ , followed by washing.

Coating with polyaniline containing the C-14 isotope is carried out by the electrochemical method from a monomer solution. Polyaniline evenly covers nanotubes. Subsequent annealing completes the formation of the composite columns of carbon nanotubes - polyaniline, which are arranged orderly on the surface of the electrode.

Example

To form a supercapacitor electrode, a buffer layer of titanium with a thickness of 20 nm and a catalytic layer of nickel with a thickness of 2 nm were deposited on a substrate of highly doped n-type silicon. After this, the substrate was placed in a magnetron and silicon oxide was deposited with a thickness of 1 μm. After that, using planar technology methods (applying and processing of photoresist, photolithography, removal of photoresist from windows, etching of windows, removal of photoresist and final washing of the substrate), windows were opened in silicon oxide. Next, the substrates were placed on the holder in the loading chamber, the loading chamber was pumped out, then, using the loading device, the samples were introduced into the reactor and placed on the surface of the working table heated to a temperature of 550 ° C. The pressure in the reactor was brought to 5 × 10 ^-3 Pa. Then, a stream of argon was passed through the reactor at a feed rate of 300 cm ³ / min, ammonia 100 cm ³ / min and acetylene 100 cm ³ / min. Immediately before the synthesis (the formation of carbon nanotubes), the pressure in the reactor was stabilized up to 400 Pa. A high-frequency plasma was generated with the supply of electromagnetic radiation with a power of 20 watts. At the end of the synthesis of carbon nanotube arrays, the flow of electromagnetic radiation, argon, ammonia and acetylene was stopped, the pressure was reduced to 5 × 10 ^-3 Pa, and the substrates were removed.

After the formation of vertically oriented arrays of carbon nanotubes, heat treatment was performed at a temperature of 350 ° C and a pressure of 5 × 10 ^-3 Pa.

The formed beams on the surface of the conductive plate are shown in FIG. 2. The diameter of the bundles of carbon nanotube arrays varied from 30 to 60 nm, which is consistent with the self-absorption of high-energy electrons in polyaniline.

To functionalize the surface of carbon nanotubes with carboxyl groups, a technological line for the chemical treatment of plates was used. The bottom surface of the plate was protected by chemically resistant varnish, the plate was placed in a drying chamber, the chamber was pumped out to a residual pressure of 10 Pa, the temperature in the chamber rose to 250 ° C. Drying at this temperature was carried out for 2 hours. Then a plate with an array of nanotubes was removed from the chamber. The functionalization process consisted in the chemical processing of the carbon nanotube array and was carried out in 2 stages. The first stage was the processing of carbon nanotubes in 37% hydrochloric acid for 1 hour. The plate was placed in a bath with a solution of hydrochloric acid and kept in it for 1 hour. Then the plate was removed from the bath and washed in a stream of deionized water for 10 minutes. This operation facilitates the purification of carbon nanotubes from catalyst residues. The second stage was the processing of carbon nanotubes in “aqua regia” - a mixture of concentrated sulfuric and nitric acid: (67% HNO ₃ + 98% H ₂ SO ₄ in a 1: 3 ratio). A plate with an array of carbon nanotubes was placed in this solution, which was maintained at a temperature of 60 ° C and kept in it for 2 hours. Then the carbon nanotubes were washed in deionized water at a temperature of 80 ° C for 12 hours. Then the plate was placed in a vacuum chamber, the pressure in the chamber was reduced to 5 × 10 ^-3 Pa, the chamber was heated to a temperature of 200 ° C and under these conditions the plate was held for 30 minutes. Then the chamber was cooled, the pressure in it rose to atmospheric and the plate was removed.

For the electrochemical deposition of polyaniline on a functionalized surface of carbon nanotubes, an aniline solution was prepared based on the carbon isotope C-14, sodium citrate, potassium phosphate, sodium tetraborate (weight ratio 2: 1: 1: 1) in a 0.05 molar solution of potassium chloride. To prepare a solution of potassium chloride, deionized water was used. KOH was added to the solution until the pH of the solution became 6. This solution was placed in a galvanic bath, the plate was fixed on the anode of the galvanic bath, and the anode electrode was in contact with the conductive plate. The substrate, the bottom surface of which was insulated, was placed in this solution. A potential of +300 mV was maintained on the substrate; the deposition time was 4–10 minutes. At the end of this process, the plate was removed from the plating bath, the film of chemically resistant varnish was removed mechanically, the plate was washed in deionized water for 10 hours, and then dried in vacuum at a temperature of 150-200 ° C for 24 hours.

Thus, a supercapacitor electrode was formed. For testing, the finished electrode was placed in an electrochemical cell, which served as a mockup of a supercapacitor. At first, the current drops, and then is kept constant. The constancy of current is due to the property of the supercapacitor to be charged from an internal energy source, due to beta decay of the radioactive carbon isotope C-14, which is provided by the proposed method for manufacturing the electrode.

Thus, an electrode was made, which, when placed in a mock supercapacitor, confirmed its operability and performance of the declared functions. The discharge current practically did not change, which is associated with the ability of the electrode to recharge the supercapacitor.

Claims (13)

1. A method of manufacturing a supercapacitor electrode, which consists in applying a buffer layer, a catalytic layer, then a dielectric layer on a conductive substrate, opening a window matrix in a dielectric layer to a catalytic layer with a transverse size of 40-60 microns, depositing vertically oriented carbon nanotubes in the arrays of windows, functionalizing surfaces of carbon nanotubes with oxygen-containing groups, the formation of a polyaniline layer containing the C-14 isotope on vertically oriented carbon nanotubes electrochemical deposition annealing. 2. The method according to p. 1, characterized in that the height of the carbon nanotubes is from 30 to 100 microns. 3. The method according to p. 1, characterized in that the distance between the centers of the windows is 70-100 microns. 4. The method according to p. 1, characterized in that the functional oxygen-containing group is a carboxyl group. 5. The method according to p. 1, characterized in that the thickness of the buffer layer is from 5 to 60 nm. 6. The method according to p. 1, characterized in that the buffer layer is made of aluminum and / or titanium and / or titanium nitride. 7. The method according to p. 1, characterized in that the catalytic layer is made with a thickness of from 0.5 to 20 nm. 8. The method according to p. 1, characterized in that the catalytic layer is made of iron and / or iron oxide and / or cobalt and / or cobalt oxide and / or nickel and / or nickel oxide and / or alloys. 9. The method according to p. 1, characterized in that the dielectric layer is made of silicon oxide or silicon nitride, 10. The method according to p. 1, characterized in that the dielectric layer is made of a thickness of from 0.5 to 3 microns. 11. The method according to p. 1, characterized in that the windows are square, or rectangular, or round. 12. The method according to p. 1, characterized in that it further conduct heat treatment before functionalization. 13. The method according to p. 1, characterized in that the annealing is carried out at a temperature of from 80 to 300 ° C and a pressure of from 0.001 to 1.02 bar.

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